Because of the many possible applications in terms of clamping requirements, there are nearly as many types of clamps to meet these diverse needs. Some clamping applications require clamps with long clamping arms. Other applications require clamps with offset clamping leg terminations. Certain applications require specialized clamp terminations, in order to adapt the clamp to a particular work piece. As a result, certain trades require workers to have on hand a large collection of different sizes and styles of clamps. The expense of acquiring and maintaining a large set of clamps can be considerable. Besides the cost, having numerous clamps on hand can occupy a lot of storage space.
A further drawback to currently available clamps is that the clamp's terminations do not always line up properly. This is often a result of over-tightening the clamp onto a work piece. Sprung clamps are usually discarded. Sometimes, with great difficulty, an attempt is made to realign the terminations; often, with unsatisfactory results. If a damaged clamp is not discarded, or if the repair is unsuccessful, continued use of the clamp can create a dangerous condition Misaligned terminations can cause a clamp to unexpectedly lose its hold on the one or more work pieces and injure the worker or damage some part.
One prior art clamp, which is not commercially available, discloses two means whereby locking toggle clamps may be adapted to a variety of clamping applications. In a first embodiment, clamp arm extensions are added, in an end-to-end fashion, to supposedly increase the reach of the clamping arms. This approach is impractical because the termination clamping member can only be sized to fit a similarly sized extension member. The extension members are depicted as being parallelepiped in shape, with each successive extension fitting inside the hollow end portion of its adjacent member (proximal to the handle end). Consequently, a clamp configured for a short reach (short effective arm length), would require fewer extension members; which, would, necessarily, involve extensions with larger end openings. The termination clamping members would, therefore, not properly fit any of the larger openings of the proximal extension members which are closer to the handle end of the clamp; thereby, obviating this method as a means of lengthening or shortening the effective clamp arm length, or reach of the clamp.
Even if allowances were made in the design of the prior art clamp whereby the ends of each extension was configured according to a bell and spigot arrangement, in which one end of each extension was identically sized according to a bell, and the opposing end of each extension was identically sized according to a spigot, the resulting clamping system would be cumbersome. The reach of the clamp would be increased by relatively large increments. Also, for a plurality of extensions in which there are more than two bell and spigot connections from the clamp arm to the clamping termination member, there would be an undesirable amount of slop, looseness, and an imprecise meeting of the clamp termination members due to an accumulation of clearances for each connection.
The second embodiment of the prior art clamp, according to one of its claims, entails a “. . . plurality of tubular extension members, each slidably mounted within the next adjacent extension member between extended and retracted positions for adjustably changing the effective length of said jaw members . . . ”. However, this claim is not supported by any of the included drawings. The drawing only depicts a hollow end portion in one end of each extension member. Therefore, the actual range of the clamp's reach between an extended position and the retracted position is indeterminate. Problems are presented whether or not each extension member is fully, or only partially, enclosed along its length within its adjacent proximal extension member. While a fully enclosed extension affords a more compact retracted configuration, problems would arise as to being able to extract extensions stuck, one inside another in the event one of the members were to become even only slightly bent. If some length were left exposed, as in a partially enclosed construction, the plurality of extension members would not result in a compact arrangement, even when in a retracted position. Additionally, any clamp system which has a plurality of extension members, and a gripping termination member, would introduce excessive slop when the clamp is in an extended position; as has been previously described. Further, a clamp configured to have a plurality of extensions would be heavy, bulky to use, and costly to manufacture.
Another problem with the prior art invention relates to the manner in which the first extension members are secured in the ends of the arms (jaws). A double-headed pin is used in each arm to retain the first extension members thereto. Throughout the specification, pins are described as being used in a non-removable manner. Also, the arms (jaws) are shown to have deep recesses which could never be accessed by reason of the pinned connections.
Prior art inventions, including U.S. Pat. No.: 2,474,940 to Hansen, and U.S. Pat. No.: 3,403,901 to Servadio, and U.S. Pat. No.: 5,143,359 to Bush, are representative of numerous patents which relate to mountable adapters on clamps and pliers. These devices are directed to the terminations of the clamping members in order to adapt the clamp or pliers to a variety of work piece shapes. These termination adapters are removable and interchangeable with other termination adapters and in no way reflect a desire by their inventors to accommodate a nearly infinite variety of clamping applications, particularly, offset conditions which are often encountered in clamping applications. Many times, the one or more work pieces to be gripped, or clamped, are not centered with respect to the distance between the clamp's arms. As a result, if a clamp with the requisite offset is unavailable, one or more spacers are often used to provide the necessary offset. The use of spacers is not recommended and can be hazardous to the user and others. Spacers can easily slide out of place, causing the clamp to quickly, and unexpectedly, lose its grip on the work piece; which, can cause possible physical harm to those who happen to be nearby, or damage to the clamped or other parts.
Prior art inventions do not teach, nor do they contemplate the need, or the advantages, for a means to be able to adjustably secure clamp arm extensions in a desired reach configuration as might be expected of an extendable table leg, tripod leg, or pruning pole. Prior art inventions also do not teach, or anticipate the advantages of utilizing a replaceable, or interchangeable, clamp arm extension member wherein only one extension member is in use at a time on each arm, and wherein a macro arm length adjustment is made by using a singular extension member of a longer or shorter length, and a smaller arm length adjustment is made by means of indexing the position of the one arm extension on each of the clamp's arms, or an infinitely variable adjustment of the one arm extension on each of the clamp's arms. Further, prior art inventions do not teach, nor anticipate, the advantages of incorporating at least a lockable fine adjustment range in the overall reach of a clamp for the purpose of precisely aligning the clamping legs' termination members. Still further, prior art inventions do not teach, nor contemplate, the advantages of a single, interchangeable, clamping leg member which, itself, engages at least one of the clamp's arms, without the use of an arm extension, and is adjustable in regard to varying the effective reach of a clamp.
Therefore, it is the several objects of the present invention to devise an integral clamping system whereby:    1. A simple, compact, economical, and practical clamp system which has an adjustable reach, offset, and work piece thickness capability with the least number of integrally designed interchangeable parts.    2. The clamp's reach can be adjusted in large or small increments and prevented from further inadvertent movement.    3. The overall range of the clamp's reach is variable between a maximum extended position and a minimum retracted position.    4. The clamp's reach is changed manually, without the use of any other tools.    5. The clamp's termination offset distance is infinitely variable and can be set manually without the use of any other tools.    6. The clamp is able to reliably and safely clamp onto a wide range of work piece thicknesses and can be set manually without the use of any other tools.